101. Methylmercury and climate change: effects on behaviour of Solea senegalensis

Eduardo Sampaio (1), Ana Luísa Maulvaut (1,2,3), Vanessa Lopes (3), Pedro Pousão (1), António Marques (1,2), Rui Rosa (3)*

1 Divisão de Aquacultura e Valorização (DivAV), Instituto Português do Mar e da Atmosfera (IPMA, I.P.), Av. Brasília, Lisboa 1449-006, Portugal
2 Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), University of Porto, Rua das Bragas, 289, 4050-123 Porto, Portugal
3
MARE- Marine Environmental Science Centre, Laboratório Marítimo da Guia, Faculdade de Ciências da Universidade de Lisboa, Av. Nossa Senhora do Cabo 939, Cascais 2750-374, Portugal

Background
Methylmercury (MeHg) is an extremely hazardous pollutant, highly accumulating in brain and central nervous system cells. In order to accurately anticipate future neurotoxic effects in fish, warming and acidification must be taken into account. Lateralization produces faster and more efficient responses to external stimuli, e.g. predator avoidance or prey capture. Flatfish use the bottom as camouflage, to avoid being detected by predators and preys. Consequently, disruption in bottom-choosing ability and lateralization may prove disastrous at an ecological level. Thus, we assessed effects on behaviour processes stemmed from MeHg contamination, subjected to warming and acidification stressors, in S. senegalensis.

Methods
During 28 days, S. senegalensis specimens were maintained under three factor crossed treatments: MeHg contaminated feed (uncontaminated: 0.60 µg g-1, contaminated: 8.01 µg g-1), pH (ambient CO2: 8.0, high CO2: 7.6), and temperature (ambient: 19ºC, high: 23ºC). Behaviour was assessed by calculating absolute (individual level) and relative (population level) lateralization using a detour test, as well as by habitat preference, measuring time spent (maximum 180 minutes) between two habitats: simple and complex (all tests, n=10 fish/treatment).

Findings
MeHg intake correlated with increased time spent in complex habitat, where fish could not camouflage or hide efficiently. In addition, intake of MeHg reduced absolute lateralization on each fish, consequently leading to complete loss of lateralization at populational level. Acidification also led to increased time spent in complex habitat, but only in uncontaminated treatments. Finally, temperature and acidification may interact with MeHg in reducing absolute lateralization.

Conclusions
MeHg intake reported major negative effects on both behavioural parameters tested. Climate change may also play a minor role in modulating individual fish lateralization. Regarding habitat preference, acidification effects are downplayed in the presence of MeHg. Disruption of these important behavioural processes may lead to a significant decrease in the ecological fitness of S. senegalensis.